Influenza viral infection prevailing on a worldwide scale every year causes mass infection including fatal cases. Although effectiveness of administration of an anti-influenza virus drug at an initial stage of the viral infection has been proved, the effect is reduced by half if timing of the administration is misjudged. As therapeutic drugs for influenza viral infection currently clinically used for the treatment of influenza, oseltamivir and zanamivir that inhibit the action of neuraminidase, that is, an enzyme present on the surface of influenza virus, amantadine that inhibits M2 protein of influenza virus, ribavirin of a nucleotide drug, and influenza vaccines utilizing immunity are known. There are a few drugs that are effective for influenza viral infection and have a high degree of safety, and in addition, appearance of viruses resistant to these drugs has started to be regarded as a problem, and therefore, a novel prophylactic/therapeutic drug for influenza viral infection is expected to be developed.
On the other hand, 5-ALA is known as an intermediate of a tetrapyrrole biosynthetic pathway widely present in animals, plants and fungi, and is generally biosynthesized by a 5-aminolevulinic acid synthetase from succinyl CoA and glycine. Photodynamic therapy or photokinetic therapy using the 5-ALA (hereinafter also referred to as the “ALA-PDT”) has been developed and attracts attention as a low invasive therapy in which QOL may be retained, and diagnostic/therapeutic agents or the like using ALAs or the like for a tumor have been reported. It is also known that the 5-ALA is useful as a preventing/ameliorating agent or a therapeutic agent for adult diseases, cancers and male sterility (see, for example, Patent Documents 1 to 3).